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Think Twice Before Giving Medical Marijuana to Your Pet

There are problems with the use of cannabis in veterinary medicine.

Dennis cox/123RF
Source: Dennis cox/123RF

Would a hit of marijuana help an epileptic dog or a cat with itchy skin? According to a recent article in the New York Times, the answer might well be yes. It described the beneficial effects of cannabis on medical problems in pets including seizure disorders, inflammation, anxiety, pain, and allergies. And the article was accompanied by a wonderful series of photographs of stoned out dogs and cats and even a pet box turtle in a state of total bliss. The article was largely based on interviews with animal lovers including a woman who gives hemp nibbles to her pet skunk and a dog trainer who uses a cannabis product called VETCBD to treat canine anxiety disorders.

I was intrigued with these claims. I initially became interested in the potential veterinary uses of medical marijuana several years ago when I was visiting relatives in Colorado who are in the cannabis business. They run Green Dot Labs, a company in Boulder that produces high grade medicinal cannabis extracts. And they convinced me there is good evidence that marijuana can ameliorate human afflictions such as chronic pain and symptoms of multiple sclerosis. But how solid is the evidence that marijuana is an effective treatment for physical and mental problems in our dogs and cats? And what are the potential negative impacts of cannabis on our companion animals? In examining the current state of research on pot and pets, I uncovered two problems.

Problem 1: The Evidence

Testimonials by pet owners extolling the value of cannabis as a veterinary miracle drug do not mean much when it comes to scientifically evaluating the efficacy of a new drug. Just like physicians, veterinarians value the results of clinical trials in which one group of subjects gets the drug and a control group does not. But in a thorough search of the published veterinary medical literature, I could not find a single clinical trial which has assessed the impact of any cannabis product on health problems in pets. That’s why the Food and Drug Administration has not approved the use of medical marijuana in non-human animals.

In short, other than personal anecdotes, there is no evidence that marijuana is an effective treatment for any affliction of dogs, cats, skunks, or turtles.

Problem 2: Marijuana Poisoning

While I had no luck finding research papers on the veterinary medical uses of marijuana, I did find convincing evidence that cannabis can make pets sick. A 2004 paper in the journal Veterinary and Human Toxicology spelled it out. The research was based on 213 cases of marijuana poisoning in dogs reported to the ASPCA’s Animal Poison Control Center over a three-year period. In nearly every case, the dogs showed neurological symptoms, and 30 percent of the dogs had gastrointestinal problems. The most common symptoms were depression and a sudden loss of balance and muscle coordination (ataxia). Other symptoms included vomiting, tremors, dilated pupils, muscle weakness, depressed heart rate, disorientation, and hypothermia.

A similar pattern of results was found in a more recent report in the Journal of Veterinary Emergency and Critical Care. The researchers were interested in whether the legalization of medical marijuana in Colorado had been accompanied by a jump in the number of dogs suffering from marijuana poisoning. They examined cases of THC toxicosis at two Colorado veterinary hospitals in between 2005 and 2010. (THC is a major active ingredient in marijuana). Between 2005 and 2010, 125 severely stoned dogs were brought to these two hospitals by their panicked owners. And, as

Graph by Hal Herzog
Source: Graph by Hal Herzog

the researchers predicted, the annual number of cannabis poisoning cases had quadrupled in just five years.

The two research teams found the same pattern of symptoms with couple of exceptions. Poisoned dogs in the Colorado study were more likely than the ASPCA poison control center dogs to exhibit urinary incontinence, dilated pupils, and severe hypersensitive to external stimuli. The authors suggested these differences in frequency of symptoms might be due to differences in the composition of medical marijuana in Colorado.

All of the dogs in the first study completely recovered from their exposure to pot. But, sadly, two of the dogs in the Colorado study died. Both dogs had eaten butter infused with medical grade THC mixed with chocolate. Chocolate is toxic to dogs, and both animals initially experienced symptoms of chocolate poisoning. But this was followed by a host of other symptoms that you don’t want to read about. One dog died 14 hours after eating the THC butter, while the other one hung on for a day and half. The authors admit that these deaths cannot be definitely attributed to eating THC, but they think it was probably a contributing factor.

The Take Home Messages

Claims about the healing powers of medical marijuana on the animals in our lives are not based on any scientific evidence. On the other hand, it is absolutely certain that the ingestion of marijuana can sometimes make pets (at least dogs) seriously ill and on rare occasions can lead to death. And as more states legalize medical and recreational use of marijuana, it’s likely that more and more wasted pets suffering from THC toxicosis will be showing up at veterinary hospitals.

By the way, there is no reason to believe that if you like to get stoned, so will your dog.


Janczyk, P., Donaldson, C. W., & Gwaltney, S. (2004). Two hundred and thirteen cases of marijuana toxicoses in dogs. Veterinary and human toxicology, 46(1), 19-20.

Meola, S. D., Tearney, C. C., Haas, S. A., Hackett, T. B., & Mazzaferro, E. M. (2012). Evaluation of trends in marijuana toxicosis in dogs living in a state with legalized medical marijuana: 125 dogs (2005–2010). Journal of veterinary emergency and critical care, 22(6), 690-696.

Hal Herzog is Professor Emeritus of Psychology at Western Carolina University and author of Some We Love, Some We Hate, Some We Eat: Why It’s So Hard To Think Straight About Animals.

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